Electric Powered Industrial Equipment, used in areas containing explosive or flammable materials, must be designed to prevent any operation of the equipment from igniting the atmosphere. The design and construction of EX Equipment by Miretti Americas permit their classification as Explosion Proof (EX) and enable their use in explosive and hazardous atmospheres.

Auto Ignition PointsMetal surfaces, such as electric motor housings or electrical component enclosures, may become hot and must be kept below the auto ignition temperature of the explosive atmosphere. Miretti Americas EX Equipment is designed to stay well below these temperatures.

Sparks
Sparks, either as a result of an electric arc or from static discharge, cannot be permitted in an explosive atmosphere. EX Equipment uses electrical systems in EX enclosures to eliminate electric arcs and utilize static conductive tires to eliminate static discharge.
EX EnclosuresAn EX Enclosure is a case or housing that has been tested and approved to contain electrical components or apparatus. Although the joints of EX enclosures will permit the entry of explosive vapors, the strength of the enclosures must contain any internal explosion. The enclosures of Miretti Americas EX Equipment have been hydrostatically tested for internal explosive resistance to pressures in excess of UL requirements without failure.
The joints of enclosures must also have a length and fit so that any flames occurring within the enclosure are snuffed out and hot gases are cooled before reaching the outside atmosphere.

The combustion within an Explosion Proof Enclosure is contained by strong walls and accurately fitted joints which prevent flames and hot gases from escaping.

Types of EX Enclosures
Two methods are commonly used and approved in the construction of these joints: Bolt Down Enclosures and Screw Type Enclosures.

Method One: Bolt Down EnclosureConsists of accurately ground and fitted faces clamped together with a multiplicity of bolts. Accurately machined flanges of suitable length and fit prevent escape of hot gases.

Method Two: Screw Type Enclosure

Uses accurately threaded parts with UL specified screw dimensions that have at least five full threads engaged when the joint is closed. Threaded joints provide a labyrinth path to snuff out flames and to cool gases.

Miretti Americas EX Equipment use a Bolt Down Enclosure and Screw Type Enclosures for all 36-volt systems; and the Screw Type Enclosures for all 12-volt and 24-volt systems.

Conduits, Shafts and Switches
The conduits from one housing, junction box or enclosure to another, must be sealed at one end with a special two part sealing compound capable of withstanding the pressures and temperatures expected in the event of an explosion within either the conduit or the enclosure. This prevents the passing of flames or hot gases from one enclosure to another. The conduits must also be of sufficient strength to contain the resulting pressures. It is also required that where shafts or other moving mechanical linkage pass through the walls of an enclosure, the fit and length of the orifice must not permit the passage of flames or gases to the outside atmosphere. Miretti Americas EX Equipment meets and exceeds all UL designated requirements for explosion proof construction.